2.5.5:

Gtk:
* Remove default signal handlers for new signals in 2.6, 
  because adding virtual methods to existing classes would 
  break ABI. (Murray Cumming, Bryan Forbes)
* Stock: Wrapped several new stock items. (Bryan Forbes)
* AboutDialog: Added logo_icon_name property. (Murray Cumming)
* Clipboard: Added set_can_store() overload that takes no 
  arguments. (Murray Cumming)
* ComboBox: Added unset_row_separator_func(). (Murray Cumming)
* FileChooserDialog:
  - Inherit from FileChooser interface. (Murray Cumming)
  - Added constructors which allow specifying backend. (Bryan Forbes)
* IconView: Added the properties. (Murray Cumming)
* Main: Added Main constructor that takes a Glib::OptionContext(), 
  and Main::add_gtk_option_group(option_context).
  (Murray Cumming, Bryan Forbes)
* TreeIter: Add forward_search() and backward_search() 
  overloads without the limit argument.
  (Rob Page, Murray Cumming)

Pango:
* Color: Added operator bool(). 
* Renderer: Added get_color().
  ((Murray Cumming)

Documentation:
* Added some reference documenation for the new classes,
  plus several older classes.
* Corrected documentation tarball and the link to it.
* examples:
  - Added book/dialogs/aboutdialog example.
  - Added book/buttons/filechooserbutton example.
  - Used ProgressCellRenderer in book/treeview/list example.
(Murray Cumming)